Narrow Results

Well-defined CdS branched nanorod arrays on ITO glass were fabricated via a facile one-step hydrothermal approach in large scale employing cadmium sulfide and thiourea as starting agents. Structural and morphological evolutions of CdS branched nanorod arrays were studied by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A formation mechanism of the hierarchical structure via this one-step synthesis was tentatively studied by investigating the reaction time. Tree-like nanostructures can also be obtained at relative higher reaction temperatures. As CdS can directly grow on transparent conductive substrate, the product obtained here should have potential applications in optoelectric devices such as solar cells and light sources.

In this study, surface-enhanced Raman spectroscopic (SERS) substrates with reusability were carefully fabricated and investigated. Based on a simple and cost-effective hydrothermal process, zinc sheets were used as a base for growing zinc oxide nanorods (ZnO NRs) with hexagonal structures as templates for the SERS substrates. In the experimentation, the authors explored a variation of the physical NR structures based on precursors of zinc nitrate (Zn(NO${}_3{)}_2)$: hexamethylenetetramine (HMTA) at 1:1 ratio, in aqueous solution with DI water at a concentration of 2.5–20mM. The prepared zinc oxide templates were finally decorated with gold nanoparticles (Au NPs) with the sputtering deposition for 90s in order to promote the SERS-active surface. From physical observations, the scanning electron microscopic (SEM) results showed that the ZnO NRs exhibited an increase in size from 56.4nm to 244.06nm as the solution concentration was increased. Further investigations also demonstrated that the Au-decorated SERS-active samples had the gold nanoparticles covering the top of the ZnO NRs. The prepared SERS substrates were finally measured for the Raman enhancement with methylene blue (MB) as the test molecules. The results showed that the SERS substrates could detect the Raman peaks of the MB at the limit of detection of $1\times 10^{-6}$M. In addition, the SERS substrates were tested for reusability with the UV exposure, up to at least nine cycles. This work therefore reported the progress of the fabrications of the SERS-active materials with the reusable potentials in several SERS applications.

Well-oriented TiO₂ nanorod (NR) arrays were fabricated directly on conductive side of F/SnO₂ substrates via hydrothermal technique. The effect of growth time on the TiO₂ NR thin film was examined. Field emission scanning electron microscope revealed that NRs exhibited a tetragonal structure with square top facets. Thickness measurements indicated that the thicknesses of the samples increased from 0.234$\mu$m to 1.544$\mu$m as the growth time was extended. The investigation of XRD indicates that the TiO₂ films are single-crystalline type of rutile. The effect of growth time on optical and electrical properties has been studied. With optimum growth time, dye sensitized solar cell (DSSC) efficiency of 1.48% could be reached using 1.544$\mu$m long TiO₂ NR arrays as electrode.

A carbon precursor film was formed on a titanium plate by a hydrothermal method using glucose, and an amorphous film was obtained by carbonization at 400^∘C under an Ar atmosphere. The morphology and composition of the surface was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the interface contact resistance (ICR) under different pressures by simulating the working mode of the fuel cell. The corrosion resistance of amorphous carbon coatings was tested by simulating the proton exchange membrane fuel cells (PEMC). The amorphous coating showed excellent interfacial conductivity and great corrosion resistance, with high potential application in bipolar plates of PEMFCs

In this work, ZnO nanorods (ZnO NRs) were successfully synthesized on FTO-glass via hydrothermal technique. Two steps were followed to grow ZnO NRs. In the first step, the seed layer of ZnO nanocrystals was deposited by using a drop cast method. The second step was represented by the hydrothermal growth of ZnO NRs on a pre-coated FTO- glass with the seed layer. The hydrothermal growth was conducted at 90^∘C for 2h. The resulted structure, morphology and optical properties of the produced layers were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) and UV-visible spectrophotometer, respectively. The analysis confirmed that the ZnO NRs grown by the hydrothermal method have a hexagonal crystal structure which was grown randomly on the FTO surface. The crystallite size was recorded 50nm and a slight microstrain (0.142%) was calculated. The bandgap was found to be in the range of 3.14–3.17eV. The ZnO NRs have a high density and large aspect ratio. A pH sensor with high sensitivity was fabricated using a two-electrode cell configuration. The ZnO NRs sensor showed the sensitivity of $-$59.03mV/pH, which is quite promising and close to the theoretical value ($-$59.12mV/pH).

Silver nanoparticles (Ag NPs) are prepared using two different techniques namely hydrothermal and laser ablation methods. The purpose of this study is to find a more suitable method to prepare Ag NPs through comparison that can give stable and size-controlled silver nanoparticles. Techniques used for observations are X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Comparison of results exhibited that hydrothermal process is a more suitable method to prepare silver nanoparticles with smaller uniform size and better yield as compared to laser ablation method. Also, at low temperature, NPs obtained using hydrothermal process provide better control on morphology, high purity and narrow size distribution.

In this work, morphological and physical properties of pyramid-like ZnO nanostructures fabricated on Sb-doped ZnO seeding films annealed under different atmospheres are extensively studied. The Sb-doped ZnO seeding films were first prepared by sol–gel spin coating technique onto glass substrate then annealed in nitrogen, air and argon followed by low-temperature hydrothermal process for ZnO nanostructures fabrication. The morphological results exhibit the growth of pyramid-like ZnO nanostructure with increasing density of the ZnO nanostructures. The crystal structure shows pyramid-like ZnO wurtzite hexagonal growth along the c-axis without any impurity phase. The growth of pyramid-like ZnO nanostructures is due to the high growth rate of (002) plane. Photoluminescence spectra exhibit the near-band-edge of all samples while the red emission appears in ZnO nanostructures after the hydrothermal process due to the imperfection in the crystal. The reflectance of ZnO nanostructures covers the visible region with the absorption edge of 375nm. The calculation shows the relevant energy band gaps in the range of 3.26–3.28eV. The difference in hydrothermally grown ZnO nanostructures is significantly affected by different annealing atmospheres.

The effect of iron content on the structure, morphology and magnetic properties of (Ni${}_{60}$Co${}_{40}$)${}_{100-}$${}_x$Fe${}_x$ powders synthesized by hydrothermal method has been studied. Several samples have been elaborated for different Fe content ($x$= 0, 3, 5, 7, 10 and 13.5). The as- prepared samples have been characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometry (VSM). From XRD spectra and for all Fe content, we have shown the presence of both face centered cubic (FCC) and Hexagonal (HCP) nanosized phases. The lattice parameter increases with increasing Fe content and the grains size varies with Fe content to reach a minimum value of 32 nm for (Co${}_{40}$Ni${}_{60}$)${}_{90}$Fe${}_{10}$. From hysteresis curves, we have extracted the saturation magnetization, Ms, and the coercivity, Hc. We noticed that Ms increases and then decreases as a function of Fe content. The values of Hc vary from 156 Oe to 186 Oe depending on the particles shape.

A facile and green synthetic method for the synthesis of a Ln${}^{3+}$(Eu, Tb)-doped SrMoO₄ (SMO) microcrystals were developed using an environment-friendly low temperature hydrothermal method assisting with phenol formaldehyde resin (PFr). The microcrystals show narrow distribution and uniform particle size, and strong red and green emissions from Eu${}^{3+}$ and Tb${}^{3+}$ ions, and it is selectively quenched upon addition Fe${}^{3+}$ ions, thus making the microcrystals as a potential Fe${}^{3+}$ ions sensing material, and the detection limit is nearly micromole level.

The hydrothermal method, using the template is a conspicuous way to change the morphology of the product, so it is used widely in many reports. The effect of temperature on morphology of NiCo₂S₄ by hydrothermal synthesis and its electrochemical properties is distinct as high-performance electrode materials for supercapacitors. With the help of the template (carbon sphere), different morphologies of NiCo₂S₄ under 90${}^{\circ }$C, 120${}^{\circ }$C and 180${}^{\circ }$C were obtained. They have different properties after electrochemical analysis. In order to build a hierarchical multi-level structure, two-step vulcanization was carried out at each temperature, resulting in the difference in the morphology and performance of the six sample of electrodes. The obtained NiCo₂S₄ electrodes exhibit 1000Fg${}^{-1}$ at the current density of 1Ag${}^{-1}$ in the second-step of the hydrothermal process under 120${}^{\circ }$C, which is superior to the microblocks NiCo₂S₄ electrode (90${}^{\circ }$C, 888Fg${}^{-1}$ at the current density of 1Ag${}^{-1}$) and microparticles NiCo₂S₄ electrode (180${}^{\circ }$C, 574Fg${}^{-1}$ at the same current density) in the second-step hydrothermal, which shows a high-rate capability (640Fg${}^{-1}$ at 20Ag${}^{-1}$). The obtained nanoparticles NiCo₂S₄ under 180${}^{\circ }$C in the first-step hydrothermal electrode had an excellent cycle retention rate (89.7%), although its specific capacitance was lower. At the same time, the specific capacitance of these sample electrodes obtained in the second-step hydrothermal process is superior to those from the first-step. It was mainly attributed to the fact that temperature can influence the morphology by controlling ion exchange. And our experiment aims to use the hydrothermal method and the template method to find a more suitable temperature range to provide more ideas.

Herein, $\alpha$-Fe₂O₃ hollow cage-like nanostructures were prepared via a simple in situ template-assisted hydrothermal route. The results showed that the shell and the size of the $\alpha$-Fe₂O₃ hollow nanostructures could be easily controlled by adjusting the amount of Fe source (FeCl${}_3)$. By increasing the amount of Fe source, the size increases, and the shells are built up from the dense single nanoparticle aggregations to crosslinked nanoparticle aggregations with large cavities gradually. It is found that the surface morphology has great impact on charge separation and transport of the $\alpha$-Fe₂O₃ cage-like nanostructures, too dense particle aggregations and too many large cavities are unfavorable for electron transport, only the product with an optimal primary particles and channels could exhibit good catalytic performance in photo-Fenton degradation of rhodamine B (RhB) with visible light.

The monoclinic phase of VO₂ has promising application as a smart window material because it possesses a reversible metal-to-semiconductor transformation with a critical temperature of $68^{\circ }$C. The high critical temperature must be lowered to achieve a possible application. Anion doping has been widely researched as possible doping of VO₂(M) with fluorine is the main option nowadays. However, other halogen elements such as chlorine have not been investigated albeit possessing possible advantages properties. In this work, we report the use of chlorine anion as doping for VO₂(M) to lower its critical temperature and to enhance its thermochromic performance. The synthesis was performed using a facile one-step hydrothermal reduction of vanadium pentoxide by hydrazine at 350–$490^{\circ }$C, using ammonium chloride as the source of the anion. The result showed that the optimum temperature to synthesize Cl-doped VO₂(M) was $490^{\circ }$C. The lowest critical temperature that can be achieved by chlorine-doped VO₂(M) was at $59.9^{\circ }$C. The thermochromic performance of Cl-doped VO₂(M) was improved compared to pristine VO₂(M) nanoparticle. This finding provides a novel use of chlorine-doped VO₂(M) with a facile one-step hydrothermal method to synthesize chlorine-doped VO₂(M) as well as the feasibility of chlorine-doped VO₂(M) as a smart window material.

Here, a series of Fe_x${\text{Co}}_{1-x}$S₂ ($x=0$–1) samples were synthesized by a hydrothermal approach. The bimetallic sulfides exhibited superior ORR and OER performances compared to the corresponding monometallic sulfides. Among all synthesized samples, the ${\text{Fe}}_{0.25}$${\text{Co}}_{0.75}$S₂ sample showed the best catalytic activities, indicating that the optimal properties were related to the combination amount. Similarly, thanks to the synergistic effect of bimetallic ions, the Li–O₂ batteries with ${\text{Fe}}_{0.25}$${\text{Co}}_{0.75}$S₂ cathode catalysts displayed the highest initial charge/discharge capacities and best cycle performance compared with CoS₂ and FeS₂. Moreover, the cell with ${\text{Fe}}_{0.25}$${\text{Co}}_{0.75}$S₂/Super P electrode cycled for 70 times, while the cells with CoS₂/Super P and FeS₂/Super P electrode only reached 49 and 45 cycles, respectively, at a limited capacity of 500mAh/g at 100mA/g. These results demonstrated that the combination of different element ions could be an efficient strategy to facilitate the reaction rate of ORR and OER.

It is accepted that cerium doping is a great way to stabilize the structure of metallic oxides and improve the electrochemical performance of lithium (Li)-ion batteries (LIBs). Using a simple hydrothermal method, we doped Ce into tin-based oxides and synthesized Ce-doped SnO₂@Ti₃C₂ nanocomposites with Ti₃C₂-MXene as a framework. The as-prepared Ce-doped SnO₂@Ti₃C₂ nanocomposites show higher surface area and lower Li+ diffusion barrier, and the galvanostatic charge/discharge cycle stability is better than that of SnO₂@Ti₃C₂. Additionally, the nanocomposites exhibit excellent initial discharge capacity (1482.6 mAh g${}^{-1}$) at 100 mA g${}^{-1}$ and a remarkable cycle rate performance. After 150 cycles, the achieved discharge capacity remained at 310.8 mAh g${}^{-1}$. This study provides a new method of using two-dimensional (2D) layered materials and rare earth elements as lithium-ion storage materials.

Herein, Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunctions with $Z$-type structure were successfully prepared by a one-step hydrothermal method. Moreover, the effects of different composite ratios on the properties of materials were explored. The electrochemical tests and photocatalytic degradation experiments showed that the corresponding Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunctions all exhibited improved electrochemical performance and photocatalytic performance than that of the bare Bi₂WO₆ material. Especially, when the molar ratio of Al to Bi was 2:1, the obtained Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunction displayed the optimal photoelectric and photocatalytic performance. In detail, it depicted the highest photocurrent density, the smallest resistance and the fastest charge transfer rate. What’s more, the RhB solution (10 ppm) could be completely degraded in 30 min under visible-light irradiation, and the removal rate was almost 1.6 times than that of pure Bi₂WO₆ nanosheets. In the same condition, it also exhibited excellent photocatalytic performance for the degradation of tetracycline (TC) solution (10 ppm) and the K₂Cr₂O₇ solution (40 ppm). These results fully manifested that the constructed Al₂(WO${}_4{)}_3$/Bi₂WO₆ heterojunction possessed superior photoelectric conversion capacity and outstanding photocatalytic performance. Moreover, based on the obtained experimental results, a $Z$-scheme mechanism of catalytic degradation of RhB and TC under simulated solar light was proposed and discussed.

Herein, a nitrogen, carbon co-doped anatase and rutile double-phase waxberry-shaped ${\mathrm{\text{TiO}}}_2$ composite photocatalyst is prepared with the one-step simple hydrothermal synthesis process, in which P25 was used as the precursor, and urea as the source of nitrogen and carbon. A suitable valence band position (2.52 eV) is provided by ${\mathrm{\text{N–C–TiO}}}_2$, with more active species (e.g. ${\text{h}}^{+}$, ${\text{e}}^{-}$, •$\mathrm{\text{OH}}$ and •${\mathrm{\text{O}}}_2$) being formed on the active catalysis surface, which is helpful to the redox reaction. Further comparison of experimental results ($E_g$ = 3.01 eV) proved that the novel ${\mathrm{\text{N–TiO}}}_2$ has preferable photocatalytic activity. In this study, an ingenious nitrogen- carbon co-doping structure was designed for the improvement of ${\mathrm{\text{TiO}}}_2$ photocatalytic performance, which is much for reference of this method to other photocatalyst designs.

Novel Bi₂S₃/BiOBr nanocomposites (NCs) were prepared via L-Cysteine-assisted hydrothermal avenue as efficient photocatalysts to degrade rhodamine B (RhB). As a result, the obtained Bi₂S₃/BiOBr NCs exhibited the slice-like microstructure with the average diameters of ca. 100 nm. The elemental analysis of X-ray photoelectron spectroscopy indicates that the nanocomposites were combined by Bi₂S₃ and BiOBr. Then, the photo-induced degradation of RhB was performed with a Xenon lamp to simulate the sunlight ($\lambda$> 400 nm) and the photo-decomposition rate was calculated. The following results showed that the Bi₂S₃/BiOBr NCs possessed excellent photocatalytice performance, which was better than that of other samples as control. Thus, this avenue provides a new reference for the facile synthesis of photocatalysts with low cost and high efficiency.

Constructing coupled semiconductor photocatalysts is an important approach to improve the photocatalytic activity of ${\text{TiO}}_2$. Herein, ${\text{SnO}}_2$/${\text{TiO}}_2$ composite photocatalysts were successfully synthesized through a hydrothermal method using yeast as a biological template. The as-obtained products were characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy (SEM), ultraviolet-visible spectra and nitrogen adsorption/desorption testing methods. Results showed that the nano-sized ${\text{SnO}}_2$ particles could be solvothermally synthesized at 150–180${}^{°}$C, and the C=O and C–O groups in the yeast were the main capping ligands of the ${\text{SnO}}_2$ particles, playing a key role in the synthesis of ${\text{SnO}}_2$. SEM demonstrated that the ${\text{SnO}}_2$/${\text{TiO}}_2$ composites possessed very loose structures and good uniformity. Finally, the application experiment showed that the as-obtained ${\text{SnO}}_2$/${\text{TiO}}_2$ composites exhibited exceptional effectiveness in degrading Rhodamine B.